An elastic wave resonator including comb-shaped electrodes and reflector electrodes formed on a piezoelectric substrate. In one example, an overlapping portion between the comb-shaped electrodes includes a first overlapping region and second overlapping regions. The second overlapping regions can be provided on both outside edges of the first overlapping region. In one example, the overlapping width of the first overlapping region is greater than the overlapping width of the second overlapping region, and the electrode finger pitch in the second overlapping region is greater than the electrode finger pitch in the first overlapping region.

SAW element has a substrate; an IDT having a first comb-shaped electrode and a second comb-shaped electrode located on an upper surface of the substrate; and a capacitance element located on the upper surface of the substrate. The capacitance element has a first counter electrode connected to the first comb-shaped electrode and a second counter electrode connected to the second comb-shaped electrode and facing the first counter electrode across a third gaps. The direction from the first counter electrode through the third gaps toward the second counter electrode is a reverse direction from the direction from the first comb-shaped electrode through the gaps toward the second comb-shaped electrode. If it is assumed that the gap and width of the gap are d.sub.i and w.sub.i, and the gap and width of the third gap are D.sub.j and W.sub.j, the following formula holds:
0<(W.sub.j/D.sub.j.sup.2)<2(w.sub.i/d.sub.i.sup.2).

An acoustic wave device includes: a piezoelectric substrate; and an IDT formed on the piezoelectric substrate, wherein an anisotropy coefficient is positive, an overlap region where electrode fingers of the IDT overlap each other includes a center region and an edge region, the electrode fingers in the center and edge regions are continuously formed, the electrode finger in the edge region is inclined with respect to the electrode finger in the center region so that a pitch in a width direction of the electrode finger in the edge region is greater than a pitch in a width direction of the electrode finger in the center region, and an angle between the width direction in the center region and a crystal axis orientation of the piezoelectric substrate is less than an angle between the width direction in the edge region and the crystal axis orientation.

An acoustic wave device includes first and second acoustic wave resonators with first and second IDT electrodes on a common piezoelectric substrate. A first apodization area in the first IDT electrode includes first and second edge areas with a first center area therebetween. A second apodization area in the second IDT electrode includes third and fourth edge areas with a second center area therebetween. At least one first mass-adding film is located in at least one of the first and second edge areas and overlaps the electrode fingers of the first IDT electrode, and at least one second mass-adding film is located in at least one of the third and fourth edge areas and overlaps the electrode fingers of the second IDT electrode. A thickness of the at least one first mass-adding film is equal to a thickness of the at least one second mass-adding film.